More news from the Web 2.0 Summit: Search honcho Marissa Mayer just previewed Social Search, a feature the company plans to launch as a Google Labs experiment. It’ll place user-generated content–blog posts, photos, and the like–at the bottom of search results. And that content will come from your circle of friends, which includes both people you have a direct connection with via services such as Gmail and Twitter and people those people have a direction connection with. (It’s all opt in–folks must agree to participate.)

Conference cochair John Battelle also asked Mayer about Google’s deal to put items from Twitter into its search results. She clarified the company’s plans a bit, saying it sees Tweets as a useful way to get some information on breaking news into search results before the definitive news article or blog post on the subject has been written.